MS-LS4-1: Fossil Records and Earth's History

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Geologic time Noun

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[jee-oh-loj-ik tahym]

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Geologic time

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The vast period of time covering Earth's 4.6-billion-year history, studied by geologists through rock layers and fossils.

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Example: The image shows how rock layers and fossils illustrate Earth's history over geologic time.

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Fossil Noun

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[fos-uhl]

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Fossil

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The preserved remnants, marks, or traces of ancient life-forms, such as bones or impressions, trapped within rock layers.

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Example: A fossil of a small dinosaur preserved in rock layers shows how ancient life-forms are trapped over time.

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Body fossil Noun

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[bod-ee fos-uhl]

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Body fossil

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A type of fossil formed from the actual hard parts of an organism, such as its shells, bones, or teeth.

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Example: The image shows a fossilized skeleton, illustrating how body fossils preserve the hard parts of organisms.

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Trace fossil Noun

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[treys fos-uhl]

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Trace fossil

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A type of fossil that preserves evidence of an organism's activities, including tracks, burrows, impressions, or droppings.

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Example: A dinosaur footprint in rock shows how trace fossils preserve activity evidence.

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Sedimentary rock Noun

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[sed-uh-men-tuh-ree rok]

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Sedimentary rock

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Rock formed from layers of settled particles like sand and mud, which often contains well-preserved fossils within its layers.

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Example: Layers of sediment show how sedimentary rocks form over time.

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Relative dating Noun

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[rel-uh-tiv dey-ting]

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Relative dating

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A method of determining the comparative age of rock layers and fossils without finding their exact age in years.

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Example: Fossils in deeper layers of earth are older, showing relative dating.

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Principle of Superposition Noun

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[prin-suh-puhl of soo-per-puh-zish-uhn]

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Principle of Superposition

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The scientific rule stating that in undisturbed sedimentary rock layers, the lower layers are older than the layers above them.

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Example: The image shows sedimentary rock layers, illustrating that lower layers are older than those above, demonstrating the Principle of Superposition.

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Absolute dating Noun

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[ab-suh-loot dey-ting]

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Absolute dating

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A method used to determine the actual age of a rock or fossil in years, often by analyzing radioactive isotopes.

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Example: The graph shows how a radioactive substance decreases over time, helping determine the age of rocks or fossils.

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Isotope Noun

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[ahy-suh-tohp]

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Isotope

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A form of a chemical element that has a different number of particles in its nucleus than other forms.

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Example: The diagram shows an atom with labeled protons, neutrons, and electrons, explaining isotopes as variations in neutron number.

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Radioactive decay Noun

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[rey-dee-oh-ak-tiv dih-key]

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Radioactive decay

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The process where an unstable radioactive isotope loses particles at a constant rate, changing into a different, more stable element.

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Example: A graph showing how a radioactive substance decreases over time, illustrating radioactive decay.